Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity
Microjet hydrogen flames can be directly used as micro heat sources or can be applied in micro propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of hydrogen jet flames within a mesoscale tube with an inner diameter of 5 mm was...
Main Authors: | , , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
MDPI AG
2021-07-01
|
Series: | Energies |
Subjects: | |
Online Access: | https://www.mdpi.com/1996-1073/14/15/4552 |
id |
doaj-110393699bc446db959ecc8a31982851 |
---|---|
record_format |
Article |
spelling |
doaj-110393699bc446db959ecc8a319828512021-08-06T15:21:55ZengMDPI AGEnergies1996-10732021-07-01144552455210.3390/en14154552Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero GravityJunjie Hong0Ming Zhao1Lei Liu2Qiuxiang Shi3Xi Xiao4Aiwu Fan5China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, ChinaState Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China China Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, ChinaChina Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, ChinaChina Tabacco Hubei Industrial Limited Liability Company, Wuhan 430014, ChinaState Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China Microjet hydrogen flames can be directly used as micro heat sources or can be applied in micro propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of hydrogen jet flames within a mesoscale tube with an inner diameter of 5 mm was very low. In this study, we were dedicated to improving the combustion efficiency by using a convergent nozzle (tilt angle was around 68°) instead of the previous straight one, and the exit diameter was 0.8 or 0.4 mm. The numerical results demonstrate that the maximum combustion efficiency in the case of d= 0.8 mm was only around 15%; however, the peak value for the case of d = 0.4 mm was around 36%. This happened because with d = 0.4 mm, the fuel jet velocity was around four times that of the d = 0.8 mm case. Hence, the negative pressure in the combustor of d = 0.4 mm decreased to a much lower level compared to that of d = 0.8 mm, which led to an enhancement of the air entrainment ratio. However, the highest combustion efficiency of d = 0.4 mm was still below 36%; therefore, a slightly larger tube or an even smaller nozzle exit diameter will be necessary for further improvements to the combustion efficiency.https://www.mdpi.com/1996-1073/14/15/4552combustion efficiencymicro-jet flameair entrainment ratioflame shapeflame tip opening |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Junjie Hong Ming Zhao Lei Liu Qiuxiang Shi Xi Xiao Aiwu Fan |
spellingShingle |
Junjie Hong Ming Zhao Lei Liu Qiuxiang Shi Xi Xiao Aiwu Fan Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity Energies combustion efficiency micro-jet flame air entrainment ratio flame shape flame tip opening |
author_facet |
Junjie Hong Ming Zhao Lei Liu Qiuxiang Shi Xi Xiao Aiwu Fan |
author_sort |
Junjie Hong |
title |
Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity |
title_short |
Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity |
title_full |
Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity |
title_fullStr |
Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity |
title_full_unstemmed |
Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity |
title_sort |
improvement of the combustion completeness of hydrogen jet flames within a mesoscale tube under zero gravity |
publisher |
MDPI AG |
series |
Energies |
issn |
1996-1073 |
publishDate |
2021-07-01 |
description |
Microjet hydrogen flames can be directly used as micro heat sources or can be applied in micro propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of hydrogen jet flames within a mesoscale tube with an inner diameter of 5 mm was very low. In this study, we were dedicated to improving the combustion efficiency by using a convergent nozzle (tilt angle was around 68°) instead of the previous straight one, and the exit diameter was 0.8 or 0.4 mm. The numerical results demonstrate that the maximum combustion efficiency in the case of d= 0.8 mm was only around 15%; however, the peak value for the case of d = 0.4 mm was around 36%. This happened because with d = 0.4 mm, the fuel jet velocity was around four times that of the d = 0.8 mm case. Hence, the negative pressure in the combustor of d = 0.4 mm decreased to a much lower level compared to that of d = 0.8 mm, which led to an enhancement of the air entrainment ratio. However, the highest combustion efficiency of d = 0.4 mm was still below 36%; therefore, a slightly larger tube or an even smaller nozzle exit diameter will be necessary for further improvements to the combustion efficiency. |
topic |
combustion efficiency micro-jet flame air entrainment ratio flame shape flame tip opening |
url |
https://www.mdpi.com/1996-1073/14/15/4552 |
work_keys_str_mv |
AT junjiehong improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity AT mingzhao improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity AT leiliu improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity AT qiuxiangshi improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity AT xixiao improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity AT aiwufan improvementofthecombustioncompletenessofhydrogenjetflameswithinamesoscaletubeunderzerogravity |
_version_ |
1721218562351169536 |